A droplet-shaped fuel cell flow field structure

Abstract

The present invention relates to a droplet-shaped fuel cell flow field structure, in which the flow field structure region is composed of a plurality of rows or columns of droplet-shaped flow field units alternately connected. Each droplet-shaped flow field unit includes a droplet-shaped support structure and flow channel structures on both sides of the support structure. The droplet-shaped flow field units are connected head to tail through a direct flow channel. The droplet-shaped fuel cell flow field structure of the present invention can increase the turbulence of the gas in the flow channel, has the advantages of good mass transfer effect and low pressure drop, and can significantly improve the performance of the fuel cell. At the same time, the droplet-shaped fuel cell flow field structure of the present invention is simple and easy to process, which is conducive to the large-scale production and application of fuel cells.

Description

Technical Field

[0001] The invention relates to the technical field of fuel cells, and in particular to a droplet-shaped fuel cell flow field structure. Background Art

[0002] Fuel cells are devices that can directly convert chemical energy in fuel into electrical energy. Since the process is not restricted by the Carnot cycle, they have the characteristics of high energy conversion efficiency. At the same time, because of its advantages such as low pollution emissions and environmental friendliness, the research and development of fuel cell technology has attracted much attention from governments, enterprises and researchers around the world, and is considered to be the preferred clean and efficient power generation technology in the 21st century. Among them, proton exchange membrane fuel cells also have the advantages of low operating temperature, fast room temperature start-up, no electrolyte loss, and low noise. They are considered to be the ideal power supply technology for ground transportation and portable devices. In recent years, with the continuous advancement of technology, fuel cell vehicles have gradually entered the commercial market, and there have been many successful application cases. However, their large-scale commercial application still faces two major problems: cost and life. As one of the core components of fuel cells, the flow field can reduce the processing cost of bipolar plates by optimizing the flow field structure, and at the same time improve the distribution in the battery plane, which is conducive to improving the service life of fuel cells. Therefore, improving the flow field structure of fuel cells is currently one of the main ways to reduce the cost of fuel cells and improve durability.

[0003] According to whether the velocity component facing the fuel cell membrane electrode can be generated, the flow field can be divided into two-dimensional flow field and three-dimensional flow field. Since the launch of the Mirai series fuel cell vehicles of Toyota Motor Corporation in Japan, the research and development of three-dimensional flow fields has attracted extensive attention from researchers. However, the structure of the three-dimensional flow field is complex, and the requirements for the treatment and processing of the flow field plate are high, which makes its production and processing cost high, and it is not necessarily suitable for large-scale commercial applications of fuel cells. Compared with the three-dimensional flow field, the processing technology of the two-dimensional flow field is simple, which can greatly reduce the processing cost of fuel cells and is more suitable for large-scale production. However, the traditional two-dimensional flow field for fuel cells includes parallel groove flow field, serpentine flow field, etc. The main characteristics of this type of flow field are that the turbulence of the gas in it is low, and the mass transfer mainly depends on diffusion. At high flow density, the battery is prone to shortage of raw gas and the problem of inability to discharge the product water, which limits its large-scale application in actual processes. Therefore, it is necessary to develop a flow field structure with simple processing and better mass transfer effect to adapt to the large-scale commercialization of fuel cells. Summary of the invention

[0004] The purpose of the present invention is to provide a droplet-shaped fuel cell flow field structure in order to make up for the above-mentioned technical defects, which is used to increase the turbulence of the gas in the flow field, promote the mass transfer process of reactants in the flow field under high current density, and improve the performance of the fuel cell.

[0005] The specific technical solution proposed by the present invention is as follows:

[0006] A droplet-shaped fuel cell flow field structure, the flow field structure includes multiple rows or columns of droplet-shaped flow field groups; the droplet-shaped flow field groups are connected by multiple droplet-shaped flow field units; the droplet-shaped flow field units include droplet-shaped support structures and flow channel structures on both sides of the support structures; the droplet-shaped flow field units are connected by straight channels; the flow channels on both sides of the support structure and the straight flow channels are connected, and the flow channels have a certain depth. The droplet-shaped support structure has the functions of supporting the fuel cell membrane electrode and dispersing the reaction gas, which is beneficial to increasing the turbulence degree of the reaction gas in the flow channel and promoting the mass transfer process of the fuel cell.

[0007] Based on the above solution, preferably, the structures of the alternately connected droplet-shaped flow field units are the same and the sizes are the same.

[0008] Based on the above solution, preferably, the projected shape of the droplet-shaped support structure of the droplet-shaped flow field unit on the flow field plate is a droplet shape; the droplet-shaped projected shape includes a tail and a head; the shape of the tail is a semicircle or a semi-ellipse.

[0009] Based on the above solution, preferably, the flow channel structures of the droplet-shaped flow field unit are symmetrically distributed on both sides of the droplet-shaped support structure; the widths of the flow channel structures on both sides of the support structure (d2 and d3 respectively) are equal, that is, d2 = d3; for the flow of reactants.

[0010] Based on the above solution, preferably, the width (d1) of the straight channel between the droplet-shaped flow field units is less than the sum of the widths of the flow channel structures (reaction gas flow channels) on both sides of the symmetrically distributed support structures in the droplet-shaped flow field unit, that is, d1 < d2 + d3, so that the flow velocity of the reaction gas increases when flowing through the straight channel, which helps to increase the turbulence degree of the reactants in the straight channel part.

[0011] Based on the above solution, preferably, the droplet-shaped flow field units are connected by straight channels in a head-to-tail connection manner.

[0012] Based on the above solution, preferably, there is a relative offset in the extension direction between adjacent rows or columns of droplet-shaped flow field groups, that is, between different rows or columns, and adjacent droplet-shaped flow field units are not aligned and are staggered, which helps the drainage process under the flow field ridges.

[0013] Compared with the prior art, the present invention has the following advantages:

[0014] (1) The variable diameter structure at the connection between the droplet-shaped support structure and the direct current channel of the present invention changes the gas flow cross-sectional area. Compared with the traditional two-dimensional channel structure, it increases the turbulence of the gas in the channel, improves the mass transfer capacity of the channel, and helps to improve the performance of the fuel cell at high current density.

[0015] (2) Compared with the three-dimensional flow field structure in the prior art, the droplet-shaped flow field structure of the present invention retains the flow channel structure of the reactants, can significantly reduce the pressure drop of the flow field, and greatly reduces the energy consumption of auxiliary systems such as air compressors.

[0016] (3) The variable diameter structure at the connection of the direct current channel and the staggered placement of the droplet-shaped flow field units described in the present invention can avoid the accumulation of liquid water under the wide and thick ridges, thereby improving the water management capability of the fuel cell.

[0017] (4) The flow field plate in the present invention has a simple structure, and its size and position can be adjusted according to actual conditions, which enhances the universality of the flow field structure. The convenient processing is conducive to the large-scale production and application of fuel cells. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 It is a schematic structural diagram of the droplet-shaped flow field structure according to an embodiment of the present invention;

[0019] Figure 2 It is a schematic diagram of an enlarged structure of a droplet-shaped flow field structure unit according to an embodiment of the present invention;

[0020] Figure 3 It is a structural schematic diagram of the conventional straight channel flow field described in the comparative example of the present invention;

[0021] Figure 4 The IV curve diagram of the battery of the embodiment and the comparative example;

[0022] Among them: 1. direct current channel connection structure, 2. droplet-shaped support structure, 3. droplet-shaped flow field channel. DETAILED DESCRIPTION

[0023] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail in combination with the following specific embodiments and with reference to the accompanying drawings, but the present invention is not limited to these embodiments.

[0024] Example

[0025] The embodiment of the present invention provides a fuel cell flow field plate using a droplet-shaped fuel cell flow field structure, such as Figure 1 , 2As shown, the flow field plate uses a 5 mm thick graphite plate as a substrate material, and the flow field structure area is composed of multiple rows or columns of droplet-shaped flow field units alternately connected, and the droplet-shaped flow field units are connected by a direct current connection structure 1.

[0026] The alternately connected droplet-shaped flow field units have the same structure and the same size.

[0027] The droplet-shaped flow field unit comprises a support structure 2 and a droplet-shaped flow field channel 3, and the droplet-shaped flow field channel is a reaction flow channel.

[0028] The support structure 2 of the droplet-shaped flow field unit is a droplet-shaped structure, the droplet radius r2 is 0.5 mm, and the distance from the top to the tail of the droplet is 4 times the droplet radius r2. The droplet-shaped support structure 2 has the function of supporting the fuel cell membrane electrode and dispersing the reaction gas, which is beneficial to increase the turbulence of the reaction gas in the flow channel and promote the mass transfer process of the fuel cell.

[0029] The droplet-shaped flow field channels 3 of the droplet-shaped flow field unit are symmetrically distributed on both sides of the support structure 2. The vertical distance d2=d3=1mm from the droplet-shaped flow field channel 3 to the outer edge of the droplet-shaped support structure 2 is used for the circulation of the reaction gas.

[0030] The flow field width d1 of the direct flow channel connection structure 1 between the droplet-shaped flow field units is (d2+d3) / 2, so that the flow velocity of the reactant gas increases when flowing through the direct flow channel 1, which helps to increase the turbulence of the reactant in the direct flow channel 1.

[0031] The droplet-shaped flow field units are connected end to end through a direct current channel connection structure 1 , the direct current channel connection structure 1 has a length L1 of 1 mm.

[0032] The staggered placement of the droplet-shaped flow field units between different rows or columns helps the drainage process under the flow field ridges.

[0033] The fuel cell flow field plate using the droplet-shaped fuel cell flow field structure has a flow channel processing depth of 0.4 mm and serves as the flow field plate on the cathode side of the fuel cell.

[0034] The anode flow field plate of this embodiment uses a direct current channel structure 1, and the channel depth and width are both 1 mm. The test conditions of the embodiment are as follows: the battery pressure is 50 kPa, the battery temperature is 60°C, the anode uses dry gas, the cathode uses 80% humidified air, the anode stoichiometric ratio is 2.0, and the cathode stoichiometric ratio is 3.0. The polarization curve is shown in FIG. Figure 4 .

[0035] Comparative Example

[0036] As a comparison, this comparative example will demonstrate a fuel cell flow field plate using a conventional straight channel flow field structure, such as Figure 3The fuel cell flow field plate with the direct flow channel structure has a flow channel processing depth of 0.4 mm and a flow channel width of 1 mm, and is used as the flow field plate on the cathode side of the fuel cell.

[0037] The anode flow field plate of this comparative example uses a straight channel structure, and the channel depth and width are both 1 mm. The test conditions of the embodiment are as follows: the battery pressure is 50 kPa, the battery temperature is 60°C, the anode uses dry gas, the cathode uses 80% humidified air, the anode stoichiometric ratio is 2.0, and the cathode stoichiometric ratio is 3.0. The polarization curve is shown in FIG. Figure 4 .from Figure 4 We can find that the battery performance of the droplet-shaped fuel cell flow field is much higher than that of the traditional direct current flow field, reflecting that the droplet-shaped flow field structure has excellent mass transfer and water management capabilities.

[0038] The above are only preferred specific implementation methods of the present invention and are not intended to limit the present application. Any technician familiar with the profession, without departing from the technical scope disclosed by the present invention, making slight changes or modifications using the above-disclosed technical contents are equivalent to equivalent implementation cases and should be covered within the protection scope of the present invention.

Claims

1. A fuel cell flow field, characterized in that: The flow field comprises a plurality of rows or columns of droplet-shaped flow field groups; the droplet-shaped flow field group is formed by connecting a plurality of droplet-shaped flow field units; the droplet-shaped flow field unit comprises a droplet-shaped support structure and flow channel structures on both sides of the support structure; the droplet-shaped flow field units are connected by direct current channels; The droplet-shaped flow field groups in adjacent rows or columns are relatively offset in their extending directions; The flow channel structure of the droplet-shaped flow field unit is symmetrically distributed on both sides of the droplet-shaped support structure.

2. The fuel cell flow field according to claim 1, characterized in that: The droplet-shaped flow field units have consistent structures and are the same size.

3. The fuel cell flow field according to claim 1, characterized in that: The projection shape of the support structure of the droplet-shaped flow field unit on the flow field plate surface is a droplet shape; the droplet-shaped projection shape includes a tail and a head; the tail shape is semicircular or semi-elliptical.

4. The fuel cell flow field according to claim 3, characterized in that: The widths of the flow channel structures on both sides of the support structure are equal.

5. The fuel cell flow field according to claim 1, characterized in that: The width of the direct flow channel between the droplet-shaped flow field units is smaller than the sum of the widths of the flow channel structures on both sides of the droplet-shaped support structure symmetrically distributed in the droplet-shaped flow field unit.

6. The fuel cell flow field according to claim 3, characterized in that: The droplet-shaped flow field units are connected head to tail through a direct current channel.

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